1. Field of the Invention
The present invention relates to a correction device for correcting image distortion, such as distortion aberration or chromatic aberration, produced by an optical pickup system, with respect to an image captured by a capturing element, an image processing device, an image processing method, and a capturing device.
The present invention relates to an image processing device including, for example, a processing device for creating one sheet of image from plural sheets of images captured by a capturing element, and a correction device for correcting image deterioration caused by chromatic aberration produced by an optical pickup system with respect to the captured images, an image processing method, and a capturing device.
2. Description of the Related Art
For example, in a capturing device such as a digital still camera and so on, schemes for obtaining a still image having a reduced noise in a time direction by creating one sheet of image through addition of plural sheets of captured images, have been proposed.
For example, Japanese Unexamined Patent Application Publication No. 2001-86398 discloses a sensorless vibration correction technology for still images. That is, Japanese Unexamined Patent Application Publication No. 2001-86398 discloses a method of capturing a plurality of images with a high-speed shutter operation that does not produce vibration, overlapping the captured images having low illumination, and obtaining one sheet of a still image having high illumination, in view of a vibration effect.
This technology is to reduce noise by dispersing the noise, which is a random component, through overlapping of sequentially captured images in view of noise reduction, and is closely related to a moving image frame noise reduction (NR) method. The moving image frame NR method is related to a technology overlapping a current frame on a reference frame in real time, in which the current frame and the reference frame consistently overlap one another in a 1:1 manner.
On the other hand, in the case of a still image NR, plural reference frames are typically given with respect to one sheet of a current frame. According to the still image NR method, the influence of vibration is reduced as the speed of a shutter becomes fast, and the noise reduction effect becomes large as the number of overlapping sheets of images is increased, so that high sensitivity can be expected.
A method of seeking noise reduction through overlapping plural sheets of images (hereinafter referred to as “addition NR process”), which is disclosed in Japanese Unexamined Patent Application Publication No. 2000-299874, is performed with respect to YC data (including a illumination component (Y) and a color component (C)) after a gamma correction and so on is performed, rather than a raw image from a capturing element.
Also, in a capturing device, correction of aberration occurring in an optical system is performed with respect to captured image information. A kind of aberration occurring in the optical system may be chromatic aberration of a lens. A refraction rate of a lens differs in response to wavelengths of light, i.e. colors. For this reason, focus distances differ in accordance with the wavelengths, even though the same lens is used, and thus there is a difference in size and position between images. This is called chromatic aberration.
The chromatic aberration may be divided into an axial chromatic aberration and a lateral chromatic aberration. Of these, the axial chromatic aberration causes image blurring since the focus distances of a lens differ in accordance with the wavelengths, and thus the position of an imaging plane is moved before and behind in accordance with colors.
In addition, the lateral chromatic aberration causes the magnification of an image to differ in accordance with the colors, and thus the sizes of an image on the imaging plane differ. That is, due to the lateral chromatic aberration of an image pickup lens, as illustrated in FIG. 46, optical sizes of a red component KR, a green component KG, and a blue component KB of an object OBJ, which is formed on an imaging plane PS of a capturing element, differ. As a result, for example, in the case of capturing an image of a white object, color distortion may occur, in which an edge part of its image is not white, but is dyed in rainbow colors to appear to be radially spread. The color mismatch due to the lateral chromatic aberration appears small on the optical axis of the lens, but becomes large and noticeable due to the influence of the refraction rate in a position far from the optical axis.
Diverse methods for correcting the lateral chromatic aberration with respect to image data, in addition to the correction method through study of the constitution of the optical system, have been proposed. For example, Japanese Unexamined Patent Application Publication No. 2000-299874 or Japanese Unexamined Patent Application Publication No. 2006-135805 proposes a method for correcting image deterioration caused by the lateral chromatic aberration by software.